Recently, a wordprocessor, personal computer, facsimile apparatus, or the like uses, as an information output apparatus, printing apparatuses of various schemes for printing information of a desired text or image on a sheet-shaped printing medium such as a paper sheet or film. A scheme for forming a text or image on a printing medium by applying a printing material to the printing medium has been put to practical use. A typical example of this scheme is an inkjet printing apparatus. The inkjet printing apparatus has recently improved its performance to print not only a text but also a color image.
On the other hand, along with the improvement of the performance of the color inkjet printing apparatus, it becomes common practice to execute digital image output, i.e., so-called photographic printing using the color inkjet printing apparatus. As the photographic printing becomes popular, importance has been placed on the preservative quality of an output printing medium.
Conventionally, an inkjet printing apparatus mainly uses dye inks as printing materials. However, since the preservative quality of dye inks is poor, some color inkjet printing apparatuses use pigment inks having a high preservative quality. One of remarkable phenomena especially observed in a color inkjet printing apparatus using pigment inks is “bronzing”, i.e., a colored illumination image reflected on the surface of an output printing medium. The bronzing is a disturbing element for an image observer and deteriorates the total image quality.
Some of the above-described inkjet printing apparatuses reproduce a multi-color multi-tone image using a plurality of kinds of inks by overlaying a plurality of kinds of ink dots on a printing medium, as disclosed in Japanese Patent Laid-Open Nos. 2003-54016 and 6-171111.
When colors are reproduced by discharging inks to a printing medium, occurrence of bronzing in the reproduced colors sometimes changes depending on the ink. When a color is reproduced by overlaying a plurality of kinds of inks, occurrence of bronzing in the reproduced color sometimes changes depending on the overlay order. When occurrence of bronzing in a reproduced color is better suppressed, the total image quality can be improved. Conventionally, however, the inks are not overlaid in an appropriate order considering the bronzing.